Server freezing and crashing beacuse of an average tick taking over 60 seconds

I have created myself a vanilla server (a normal, .jar one) on a 16w03a snapshot version. I made a batch file, that would run the server for me (i added some more code, to ask me, to check connetions, restart the server, etc., i have the copy in the attachment), and after running the server, it just freezes. I attached here the crash log, and the batch file i made. Just right click it, and press Edit (Arisa deleted that file, nevermind). I used from 512M to 1024M. I tried to get more (1G to 2G), but it won't let me.
(_Error ocurred while initialisation of VM_
_Could not reserve enough space for 2097152KB object heap_)
What an awkward error...